Re: [PATCH 0/6] Intel Color Manager Framework

Sharma, Shashank
2014-02-25T03:56:59Z

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Thanks for your comments Stéphane
Please find mine inline.

In general, I got the overall recommendations that if this implementation comes from generic DRM property, it would be easy to club with general interfaces, and atomic modeset calls.
I will work on this, and will come back with modified patches.

Regards
Shashank
From: Stéphane Marchesin [mailto:stephane.marchesin@gmail.com]
Sent: Monday, February 24, 2014 9:35 AM
To: Sharma, Shashank
Cc: Ville Syrjälä; Intel Graphics Development; Shankar, Uma; dri-devel@lists.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH 0/6] Intel Color Manager Framework

>+1. We'e looking into hooking up color correction controls, and if the interface isn't standard our user space won't be portable across drivers. There are multiple reasons for using drm properties:
>- the KMS interface already provides a way to set the gamma ramp, which this code seems to replicate.
>The current KMS interface just initializes the gamma soft LUT palette registers, in 8 bit mode corresponding to unit gamma. It's impossible to apply accurate values corresponding to gamma=2.2 or 1.5 from KMS
>Because for that we need to program palette registers in 10.6 bit mode of hardware.
>Then the existing interface should be extended. Otherwise you have two ways to do the same thing...

Agree.

>- the KMS interface allows us to name properties independently and enumerate them. It seems like right now you can't enumerate properties or guess what "property 0" is. I'd rather set the "Color conversion matrix" than remember to set >"property 0" (and even then, I'm not really sure it exists).

All the properties are getting enumerated in color manager register function. The framework defines proper identifiers and mapping for each property, and every property is having a corresponding soft-lut to be loaded with correction values.
Correct me if I'm wrong, but I don't see a way for user space to query the presence/absence of a given property. KMS allows that.
The color manager read function dumps the no of properties, and current status of the property. But I agree its better interface to have it in form of property, as far as the central control is concerned.

- you can reuse the get/set infrastructure which is already in place

>Another thing that came out of the discussion on irc is that we should standardize the properties. For example we could use a text file describing the name of the controls and the format of the data (something similar to the device tree >bindings). That way user space can expect "color conversion matrix" to mean the same thing everywhere, to get the same data as input, and to work the same way on all platforms.
If you can please have a look on the header file, we are almost doing the same thing, in form of a protocol.
>This protocol however is not extensible. With the KMS interface I can already do the following from user space:
>- query the existence of a given property
>- set each property in a portable fashion (for example the same gamma ramp code works on all DRM drivers)
>- easily match properties to a given crtc

Actually each of this is possible from color manager read/write, read dumps information per pipe basis.

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